1. Technical Field
The present invention relates to a bipolar lightning rod apparatus and, more particularly, to a bipolar lightning rod apparatus capable of increasing discharge efficiency for a lightning current of the falling of a thunderbolt and also preventing the coupling and fixation power of the bipolar lightning rod apparatus from becoming weak due to vibration attributable to external environment factors, such as an earthquake or a typhoon.
2. Description of the Related Art
In general, a lightning rod apparatus is installed on top of a building in order to safely discharge electric charges, accumulated in thunderclouds, to the ground by forming a discharge path between the thunderclouds and the ground.
When a thundercloud approaches the ground, a potential between the thundercloud and the ground reaches one hundred million voltages (V).
An insulating breakdown, that is, the falling of a thunderbolt is rarely generated between the ground and a thundercloud because the air of the atmospheric layer serves as an excellent insulator, but there is always a possibility that the falling of a thunderbolt may occur between the thundercloud and the ground.
In order to prevent damage attributable to the falling of a thunderbolt, a lightning rod apparatus using an electric field phenomenon (i.e., tip effect) in which an electric field is concentrated on a pointed head has been known. Such a lightning rod apparatus is called a Franklin null method.
A conventional lightning rod apparatus is described below with reference to FIG. 1.
As shown in FIG. 1, the conventional lightning rod apparatus includes a fixation unit 31 installed on top of a building and connected to ground means, a rod 30 configured to have one end fixed to the fixation unit 31 and charged with the electric charges of the ground, a rod cap 32 connected with the other end of the rod 30 and induce the falling of a thunderbolt, an insulator 34 connected to the other end of the rod 30, and electrification means 45 mounted on the rod 30. The rod 30 is placed at the center of an electrification tube 45a. 
The electrification means 45 includes an electrification tube 45a configured to have a tubular form, have the rod 30 penetrate the center of the electrification tube 45a, and have needle-shaped tips 45b formed therein and directed toward the rod 30 and a first cap 45c and a second cap 45d configured to combine both ends of the electrification tube 45a with the rod 30. The second cap 45d is closely adhered and fixed toward the insulator 34 by means of a stopper 46.
The conventional lightning rod apparatus, however, is problematic in that discharge efficiency is low because the time taken to discharge a lightning current is long due to the rod cap 32 having a relatively very smaller discharge area than the insulator 34.
Furthermore, the conventional lightning rod apparatus is problematic in that coherence between the rod 30 and the rod cap 32 is weak against vibration attributable to external environment factors, such as an earthquake or a typhoon, and coherence between the rod 30 and the fixation unit 31 is also weak because the rod 30 and the rod cap 32 have a coupling structure using a screw-mating method.